<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0607</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2026-04-17</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001119639</issuerCik>
        <issuerName>PETROBRAS - PETROLEO BRASILEIRO SA</issuerName>
        <issuerTradingSymbol>PBR</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002132041</rptOwnerCik>
            <rptOwnerName>Mello Guilherme Santos</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>true</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>28, HENRIQUE VALADARES AVE</rptOwnerStreet1>
            <rptOwnerStreet2>19TH FLOOR, A TOWER</rptOwnerStreet2>
            <rptOwnerCity>RIO DE JANEIRO</rptOwnerCity>
            <rptOwnerNonUSStateTerritory>RJ</rptOwnerNonUSStateTerritory>
            <rptOwnerCountry>D5</rptOwnerCountry>
            <rptOwnerZipCode>20231-030</rptOwnerZipCode>
            <rptOwnerStateDescription>BRAZIL</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <ownerSignature>
        <signatureName>Guilherme Santos Mello</signatureName>
        <signatureDate>2026-04-29</signatureDate>
    </ownerSignature>
</ownershipDocument>